共查询到20条相似文献，搜索用时 46 毫秒
1.
When subjected to a very high-pH, most of the soil minerals undergo physico-chemical transformation. This could induce strong modifications of the shear strength behaviour of the soil. This issue is of high interest in the framework of the design of deep nuclear wastes repositories, since the degradation of the concrete lining of deep galleries after thousands of years will generate an alkaline solute (pH > 12) that would circulate through the backfill, and alter its hydromechanical characteristics. A study was undertaken to assess the impact of high-pH fluid circulation on the shear strength behaviour of a backfill material. Because of the complexity of the existing constitutive theories, a new approach was used, based on evolutionary polynomial regression (EPR), for modelling of these processes. EPR is an evolutionary data mining technique that generates a transparent and structured representation of the behaviour of a system directly from data. An EPR model was developed and validated using results from a comprehensive set of triaxial tests. Through a sensitivity analysis, the EPR model permitted to identify the specific surface, and to a lesser extent the micropore void ratio, as coupling parameters between hydromechanical behaviour alteration during alkaline fluid circulation and a physical process. 相似文献
2.
The shear stress–strain behaviour and shear strength parameters of the interface between cemented paste backfill (CPB) and rock are of practical importance in the optimal and safe design of CPB structures. An understanding of the shear behaviour and properties at this interface is also required to develop comprehensive interface models for CPB-rock analyses, interface design methods for the static and dynamic stability analysis of CPB structures, and building high performance CPB structures. In this study, direct shear tests were conducted to investigate the interface shear strength behaviour between CPB and rock. All tests were carried out in a standard direct shear test apparatus for a range of curing ages of 1 to 28 days for the CPB. The procedures of the laboratory tests will be described. Results will be presented for interface shear behaviour, including stress–strain curves, vertical deformation and shear strength parameters. The test results show that the shear strength parameters and behaviour of the CPB-rock interface are time-dependent and significantly influenced by the normal load. 相似文献
3.
Understanding the shear behaviour of the interface between cemented tailings backfill and retaining wall structures (barricades,
bulkheads) is important for the optimal design of barricades or bulkheads, and for mine operators to balance strength and
safety against cost. However, our understanding of the shear behaviour of the aforementioned interface is limited. This paper
is aimed at investigating the interfacial behaviour and properties of cemented tailings backfill-retaining wall structures,
including stress–strain behaviour, cohesion, friction angle and shear stiffness through direct shear tests. Two different
types of barricade or bulkhead materials (brick and concrete) are used in this study. Interface shear tests are performed
at various curing times of the cemented backfill. Valuable results are obtained with regards to the interface shear behaviour
of backfill-retaining structures. Based on these results, interfacial properties between cemented tailings backfill and barricades
or bulkheads show a significant time-dependent variation. 相似文献
4.
安哥拉Quelo砂抗剪强度特性试验研究 总被引：1，自引：0，他引：1
基于安哥拉Quelo（Muceque）砂原状土和重塑土的直剪试验,探讨了结构性、含水率、干密度对Quelo砂抗剪强度的影响。试验结果表明,结构性对Quelo砂的抗剪强度影响较为复杂,原状土与重塑土的抗剪力学指标具有明显差异;Quelo砂遇水软化特性显著,原状土和重塑土的黏聚力和内摩擦角随含水率的增大近似呈对数衰减;Quelo砂级配良好,压实后抗剪强度高,适宜用作回填材料,重塑土的黏聚力随干密度的增大近似呈线性增大,内摩擦角随干密度的增大分为稳定段和增大段,呈分段函数的特征。 相似文献
5.
针对不同加砂比例的云南红土,在相应最优含水率及最大干密度的初始条件下,采用土工试验与相关理论研究相结合的方法,运用Excel分析试验数据,揭示干湿循环作用与加砂红土物理力学特性变化之间的关系。结果表明:在干湿循环过程中,不同加砂比例的红土比重均呈先上升后下降的趋势,干密度均呈上升趋势,抗剪强度及抗剪强度参数均呈下降趋势,并最终都在循环10次左右趋于稳定。在干湿循环次数一定条件下,加砂比例越大的红土,其黏粒降幅越小,粉粒和砂粒增幅也越小,裂隙数量越少,土样越密实。抗剪强度及抗剪强度参数降幅最大的是加砂比例为15%的红土,降幅最小的是加砂比例为10%的红土。 相似文献
6.
钱塘江冲海积粉土剪胀性三轴试验研究 总被引：1，自引：0，他引：1
钱塘江两岸广泛分布着冲海积粉土.通过大量的三轴固结不排水CU和固结排水CD试验,探讨饱和粉土的应力应变性状和剪胀特性。试验表明,钱塘江冲海积粉土显著的特性之一是在剪切中膨胀,剪胀主要与粉土的密度和围压有关。CU试验中密(e=0.739～0.866)的原状样在围压600kPa范围内剪切膨胀,稍密(e=0.890～0.906)的击实样在围压低于400kPa剪切膨胀。由于粉土膨胀的本质不排水强度在剪切中保持增加,对于这种情况就没有惟一的"不排水强度";CD试验稍密(e=0.889～0.945)的击实样在围压低于400kPa时剪切膨胀。钱塘江冲海积粉土的剪切破坏要经历一个大的变形过程,固结排水剪切过程的应力应变性状可分为4个阶段。取应变继续而没有进一步体积变化的临界状态做破坏标准,确定粉土排水剪切强度指标较合理。 相似文献
7.
Umashankar Balunaini Sungmin Yoon Monica Prezzi Rodrigo Salgado 《Geotechnical and Geological Engineering》2014,32(2):505-523
Use of tire shred–soil mixtures as backfill materials in mechanically stabilized earth walls has several advantages over other backfill materials: (1) good drainage, (2) high shear strength, and (3) low compacted unit weight. This paper presents the results of laboratory pullout tests performed on uniaxial geogrid embedded in tire shred–sand mixtures. The effects of tire shred size, tire shred–sand mixing ratio and confining pressure on the interaction between the geogrid and tire shred–sand mixtures are evaluated. Three sizes of tire shreds are considered: tire chips (with 9.5 mm nominal size), tire shreds 50-to-100 mm long and tire shreds 100-to-200 mm in length, with mixing ratios of 0, 12, 25 and 100 % of tire shreds in the mixtures (by weight). Based on compaction testing of a number of mixtures, the optimal mixing proportion of tire shreds and sand was found to lie between 25/75 and 30/70 (by weight of tire shred and sand); this is equivalent to approximately 40/60 and 50/50, respectively, by volume of tire shreds and sand. The pullout resistance of a geogrid embedded in tire shred–sand mixtures is significantly higher than that of the same geogrid embedded in tire shreds only. The size of the tire shreds has negligible effect on the pullout resistance of a geogrid embedded in mixtures prepared with either low (12/88 mix) or high (100/0 mix) tire shred content. However, when the 25/75 mixture is used, greater geogrid pullout resistance was obtained for the geogrid embedded in tire chip–sand mixtures than in tire shred–sand mixtures. 相似文献
8.
Liu Xiaoyan Congress Surya Sarat Chandra Cai Guojun Liu Songyu 《Acta Geotechnica》2021,16(5):1487-1507
Buffer/backfill material is an important engineering barrier in a deep geological repository of high-level radioactive waste (HLW). Its thermo-hydro-mechanical (THM) performance is very important for the safe and stable operation of the HLW repository system. Natural graphite powder mixed with sodium bentonite forms a buffer/backfill material that can dissipate heat quickly and provide strong isolation. In this paper, the THM characteristics of bentonite–sand–graphite–polypropylene fiber (BSGF) mixtures, used as a buffer/backfill material, were studied through a series of laboratory tests. The influence of graphite and polypropylene fiber contents on thermal conductivity, swelling pressure, hydraulic conductivity, and strength properties of BSGF mixtures with different sand contents was analyzed. Experimental results indicated that the graphite content, the maximum graphite mesh number, and the initial dry density of bentonite–graphite mixtures influenced the thermal conductivity of bentonite–graphite mixtures. The addition of polypropylene fiber was found to enhance the shear strength and inhibit cracking without significantly affecting the expansivity, permeability, and thermal conductivity of the BSGF mixtures. This study provides a new buffer/backfill material that can improve the stability, functionality, and thermal efficiency of the HLW repository.
相似文献9.
Mahmoud Ghazavi 《Geotechnical and Geological Engineering》2004,22(3):401-416
Waste materials such as waste tires, rubbers, and plastic materials are normally produced in every society, entering the environment
and causing serious problems. These problems may be somehow reduced by finding applications for them in engineering, for example,
as lightweight materials for backfill in geotechnical projects. To this aim, this paper demonstrates how shear strength characteristics
of sand mixed with various percentages of waste garden hose grains are altered. A relatively, uniform sand has been mixed
with waste hose grains in loose and slightly compacted states. Waste hose grains were prepared with special popular machinery
in a local area. Various sand-rubber mixtures having 0%, 10%, 15%, 20%, 50%, 70%, and 100% waste hose particles by weight
were chosen. The rubber grains were distributed in the sand such that uniform mixtures are obtained. In order to compare the
shear strength of different sand-rubber samples, two compaction states were considered. The results show that the influencing
parameters on shear strength characteristics of sand-rubber mixtures are normal stress, mixture unit weight, and rubber content.
With the selected waste hose particles, compaction states, and rubber contents, the initial friction angle φ1 does not change significantly. However, an apparent cohesion appears in the mixtures. From environmental point of view and
due to lightweight material for the sand-waste hose particles, it may be useful to use such materials in corresponding geotechnical
projects.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
There is a pressing need of finding innovative and beneficial ways of using scrap tires in the construction of various geotechnical
structures because a large number of waste tires are generated and discarded every year throughout the world. One example
of such geotechnical application is the use of tire shreds mixed with soil as a backfill material for mechanically stabilized
earth (MSE) walls. In this paper, we report the results of laboratory pullout tests performed to study the interaction between
ribbed-metal-strip reinforcement and tire shred–sand mixtures prepared with various tire shred sizes (9.5 mm in nominal size,
50–100 mm in length, and 100–200 mm in length) and tire shred-to-sand mixing ratios (tire shred contents of 0, 12, 25, 100%
by weight). The pullout capacities of ribbed metal strips embedded in tire shred–sand mixtures were obtained for three confining
pressures (40, 65, and 90 kPa). The test results showed that the pullout capacity of ribbed metal strips embedded in tire
shred–sand mixtures is much higher than that of ribbed metal strips embedded in samples prepared with only tire shreds. Based
on the laboratory pullout test results, an equation was developed that can be used to estimate the pullout capacity of ribbed
metal strips embedded in tire shred–sand mixtures if the tire shred size, compacted unit weight of the mixture, mean particle
size of sand, and vertical effective stress acting at the interface are known. 相似文献
11.
To enhance the understanding of thermal impact on the in situ behaviour of the Callovo–Oxfordian argillite, this paper presents an interpretation of an in situ heating experiment carried out in the Meuse/Haute Marne Underground Research Laboratory (M/HM URL). The argillite was heated successively by two constant heating powers: 277 W and 925 W. When subjected to thermal loading, the argillite exhibits an important volume change and a strong pore pressure response that significantly affect its hydraulic and mechanical behaviour. Numerical analysis has been performed by using a coupled theoretical formulation that incorporates a constitutive model especially developed for this material. Based on Biot's theory, this model includes the influence of interstitial pressure on the mechanical behaviour. The simulation obtained reproduces satisfactorily the results of the in situ experiment and the main observed patterns of behaviour. The interpretation and discussion of numerical results provide additional data that can help us to understand the thermo-hydromechanical behaviour concepts of saturated argillite formation. 相似文献
12.
Classification,shear strength,and durability of expansive clayey soil stabilized with lime and perlite 总被引：1，自引：0，他引：1
An experimental study was performed to investigate the effect of perlite and perlite–lime admixtures on classification, shear strength, and durability properties of an expansive soil containing smectite clay minerals. Two types of mixtures, namely soil–perlite and soil–perlite–lime, were prepared with different percentages of perlite and compacted with standard Proctor energy at their optimum water contents. Samples of 38 mm diameter and 76 mm height for durability tests and square samples of 60 mm edge for shear box test were taken and preserved until test time in a desiccator. Disturbed samples were also taken to determine liquid and plastic limits. The expansive soil shows behavior of fine sand and silt due to pozzolanic reactions in microstructure caused by addition of lime and perlite. Although apparent cohesion of treated soil decreased with increasing amount of perlite for both types of samples, perlite–lime-treated samples had higher apparent cohesion than only perlite-treated samples. Large increments in angle of shearing resistance were obtained with increasing usage of perlite. Samples stabilized with only perlite could not show enough durability at the durability tests based on volumetric stability and unconfined compression strength. However, samples stabilized with lime and more than 30 % perlite proved to have enough durability and shear strength. 相似文献
13.
Cemented coarse-grained alluvium is present in a vast area of Tehran city, Iran including its suburbs. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of triaxial compression tests were performed on uncemented, artificially cemented and destructured samples. Hydrated lime was used as the cementation agent for sample preparation to model the Tehran deposit. The tests were performed on cemented samples after an appropriate time for curing. The tests on cemented samples show that a shear zone appears as the shear stress approaches the peak shear strength. During shearing these samples undergo dilation at confining stress lower than 1000kPa. However, the uncemented and destructured samples show contraction during shearing. Peak shear strength is followed by strain softening for all cemented samples. The shear strength increases with increasing cement content but the influence of the cementation decreases as the confining stress increases. With increasing cementation the stress-strain behaviour of samples tend towards the behaviour expected of high-density soils. Test results indicate that the failure envelope for cemented samples is curved and not linear. 相似文献
14.
Shear Behaviour of Loose and Compacted Pond Ash 总被引：1，自引：0，他引：1
Massive utilization of pond ash in earth works requires thorough understanding of its geotechnical characteristics, especially
strength characteristics. Here in this paper, a detailed experimental study carried on the strength and other geotechnical
characteristics of pond ash samples, collected from inflow and outflow points of two ash ponds in India, are presented. Strength
characteristics were investigated using consolidated drained (CD) and undrained (
[`(\textCU)] \overline{\text{CU}} ) triaxial tests with pore water pressure measurements, conducted on loose and compacted specimens of pond ash samples under
different confining pressures. Ash samples from inflow point exhibited behaviour similar to sandy soils in many respects.
They exhibited higher strengths than reference material (Yamuna sand), though their specific gravity and compacted maximum
dry densities are significantly lower than sands. Ash samples from outflow point exhibited significant differences in their
properties and values, compared to samples from inflow point. Shear strength of the ash samples from outflow point are observed
to be low, particularly in loose state where static liquefaction is observed. 相似文献
15.
Use of scrap tyres in isolation systems for seismic damping, requires a knowledge of the engineering properties of sand–rubber mixtures (SRM). The primary objective of this study is to assess the influence of granulated rubber and tyre chips size and the gradation of sand on the strength behaviour of SRM by carrying out large-scale direct shear tests. A large direct shear test has been carried out on SRM considering different granulated rubber and tyre chip sizes and compositions. The following properties were investigated to know the effect of granulated rubber on dry sand; peak shear stress, cohesion, friction angle, secant modulus and volumetric strain. From the experiments, it was determined that the major factors influencing the above-mentioned properties were granulated rubber and tyre chip sizes, percentage of rubber in SRM and the normal stress applied. It was observed that the peak strength was significantly increased with increasing granulated rubber size up to rubber size VI (passing 12.5 mm and retained on 9.5 mm), and by adding granulated rubber up to 30%. This study shows that granulated rubber size VI gives maximum shear strength values at 30% rubber content. It was also found that more uniformly graded sand gives an improved value of shear strength with the inclusion of granulated rubber when compared to poorly graded sand. 相似文献
16.
The Mechanical Behaviour of a Pyroclastic Rock: Yield Strength and “Destructuration” Effects 总被引：1，自引：0，他引：1
Summary
A research programme on the mechanical behaviour of a homogenous volcanic tuff found in the centre of the city of Naples (Italy)
was carried out at the University of Naples a few years ago. Isotropic and drained triaxial tests were performed in a very
wide range of confining pressures (up to 60 MPa). After presenting the stress-strain curve pattern and the mean stress influence
on the shear behaviour, the paper focuses on the definition of a strength criterion and of the yield surface for this material.
Some tuff samples were subjected to isotropic compression tests up to a confining pressure approximately twice as high as
the isotropic yield stress; they were subsequently unloaded and subjected to drained triaxial tests. Partial loosening of
the interparticle bonds (“destructuration”) was observed. The paper also compares the mechanical behaviour of intact and “destructured”
samples, emphasising the effects of the structure on strength and yield. 相似文献
17.
A technique has been developed to control the strength of moistened sand in a quantifiable, accurate and reproducible way, while other mechanical properties were maintained. Strength of dry sand was increased through adding a small amount of liquid. In order to control the additional cohesion of moist sand, the influence of the surface tension of the liquid was investigated. Direct shear experiments were performed on four granular materials at confining stress levels below 1 kPa. It has been found that the surface tension of the added liquid controlled the additional apparent cohesion of sand with high accuracy. The mechanical properties of moist sand show dynamic similarity towards natural brittle rock, which enables analogue modelling of fault formation, fault reactivation and tension fracture formation in the brittle regime with a controlled strength profile. Furthermore, experimental results fit well to shear strength models. From this followed the direct proportionality of the unsaturated shear strength parameter φb relative to the matrix suction, measured at low stress levels. Moreover, shear strength turned out to be also a function of grain size and the grain shape. 相似文献
18.
Cui Ming-Juan Zheng Jun-Jie Dahal Bhim Kumar Lai Han-Jiang Huang Zhan-Fang Wu Chao-Chuan 《Acta Geotechnica》2021,16(5):1429-1439
Calcareous sand, a special type of sand commonly used for the construction of coastal engineering in tropical coasts, is usually required to be strengthened due to its poor engineering mechanical properties. Microbially induced carbonate precipitation has been proved to be a promising method for this purpose. A higher cementation level generally leads to a greater strength enhancement, but tends to cause brittle failure of bio-cemented calcareous sand, which in turn brings great potential risks for the coastal engineering. Therefore, the shear behaviour, especially the brittle behaviour, of bio-cemented calcareous sand needs to be understood properly, and taking some measures to improve its brittle behaviour is also necessary. In this regard, a series of triaxial compression tests were conducted to study the shear behaviour of bio-cemented calcareous sand with various cementation levels, and the waste rubber particles are used to improve the brittle behaviour of bio-cemented calcareous sand. The test results show that the shear strength of bio-cemented calcareous sand increases with the increase in cementation level, and the brittle behaviour is significant gradually. The waste rubber particles contribute to improve the brittle behaviour of bio-cemented calcareous sand, reducing the dilation of bio-cemented calcareous sand and slowing the changes in dilatancy with the increment of stress.
相似文献19.
Callovo-Oxfordian (Cox) argillite was investigated in the context of feasibility studies for an underground repository for nuclear waste. In this study, the influence of mineralogical composition and water content on the mechanical properties of the Cox argillite was investigated. The samples were drilled from three representative depths at which the rock formations have different mineralogical compositions. Micro-indentation and mini-compression tests were performed on samples with different water contents. The elastic and failure properties of argillite were determined and were found to be related to the mineralogical composition and water content. Both the elastic modulus and strength decrease with increasing clay and water contents. 相似文献
20.
Hanifi Missoum Mostefa Belkhatir Karim Bendani Mustapha Maliki 《Geotechnical and Geological Engineering》2013,31(1):279-296
In a number of recent case studies, the liquefaction of silty sands has been reported. To investigate the undrained shear and deformation behaviour of Chlef sand–silt mixtures, a series of monotonic and stress-controlled cyclic triaxial tests were conducted on sand encountered at the site. The aim of this laboratory investigation is to study the influence of silt contents, expressed by means of the equivalent void ratio on undrained residual shear strength of loose, medium dense and dense sand–silt mixtures under monotonic loading and liquefaction potential under cyclic loading. After an earthquake event, the prediction of the post-liquefaction strength is becoming a challenging task in order to ensure the stability of different types of earth structures. Thus, the choice of the appropriate undrained residual shear strength of silty sandy soils that are prone to liquefaction to be used in engineering practice design should be established. To achieve this, a series of undrained triaxial tests were conducted on reconstituted saturated silty sand samples with different fines contents ranging from 0 to 40 %. In all tests, the confining pressure was held constant at 100 kPa. From the experimental results obtained, it is clear that the global void ratio cannot be used as a state parameter and may not characterize the actual behaviour of the soil as well. The equivalent void ratio expressing the fine particles participation in soil strength is then introduced. A linear relationship between the undrained shear residual shear strength and the equivalent void ratio has been obtained for the studied range of the fines contents. Cyclic test results confirm that the increase in the equivalent void ratio and the fines content accelerates the liquefaction phenomenon for the studied stress ratio and the liquefaction resistance decreases with the increase in either the equivalent void ratio or the loading amplitude level. These cyclic tests results confirm the obtained monotonic tests results. 相似文献